The HO2S is used to supply the PCM with information regarding the composition of the air/fuel mixture. The HO2S is positioned in the exhaust pipe ahead of the TWC. To measure the oxygen content, the HO2S requires a supply of ambient air as a reference. The HO2S produces a voltage that varies between 0.1V and 0.9V under normal operating conditions. The Powertrain Control Module (PCM) monitors this voltage and determines if the exhaust gas is lean or rich. If the voltage input at the PCM is under approx. 0.45V the exhaust is lean, and if the voltage input is over approx. 0.45V the exhaust is rich. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
If HO2S signal voltage has continued to higher than 1.2V, the PCM determines that a fault exists and a DTC is set.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Circuit voltage is monitored | ● Poor connection ● Short to battery in HO2S circuit ● Faulty HO2S ● Faulty PCM |
Enable Conditions | ● Engine coolant > 81℃ | |
● Engine speed >1187rpm | ||
● Load value >300mmHg | ||
Threshold value | ● Circuit voltage after applying 5V to sensor ≥ 4.5V | |
Diagnosis Time | ● Continuous |
signal voltage | Normal parameter |
voltage will vary between 0.1 and 0.9V |
